Examining the effects of pressure on iron-based effects

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image: Experimental equipment: The diamond anvil cell (left) and hydrostatic pressure cell (right) can be used to establish the effect of pressure on the superconducting material.
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Credit: FLEET

The discovery of iron-based superconductors with a relatively high transition temperature Tvs in 2008 opened a new chapter in the development of high temperature superconductivity.

The following decade saw a “research boom” in superconductivity, with remarkable achievements in the theory, experiments and applications of iron-based superconductors, and in our understanding of the fundamental mechanism of superconductivity.

A UOW article published last month reviews the progress of high-pressure studies on the properties of iron-based superconductor (ISBC) families.

FLEET doctoral student Lina Sang (University of Wollongong) was the first author on the Materials Today Physics journal article, studying the effects on superconductivity, flux trapping, and vortex dynamics of VSI materials, including:

  • pressure-induced superconductivity
  • increase in transition temperature Tvs
  • superconductivity pressure induced elimination / re-emergence
  • effects of phase separation on superconductivity
  • increase in critical current density
  • significant suppression of vortex creep
  • reduce the size of the flux beams.

The review highlights the use of pressure as a versatile method to explore new materials and better understand the physical mechanisms of high temperature superconductors.

SUPERCONDUCTORS: A HISTORY

In a superconductor, an electric current can flow without any loss of energy to the resistance.

Iron-based superconductors are a type of “high temperature” superconductor (type II or unconventional) in that they have a transition temperature (Tvs) well above a few degrees Kelvin above absolute zero.

The driving force behind these Type II superconductors has remained elusive since their discovery in the 1980s. Unlike “conventional” superconductors, it is clear that they cannot be directly understood from the theory of BCS electron-phonon coupling. (Bardeen, Cooper and Schrieffer).

In successive discoveries, the transition temperature Tvs has been driven consistently higher.

“The ultimate goal of superconductivity research is to find superconductors with a superconducting transition temperature (Tvs) at room temperature, ”explains Professor Xiaolin Wang, node manager and FLEET theme manager (also at Wollongong University) and Dr Sang’s thesis director.

“The pressure can dramatically increase the Tvs for Fe-based superconductors. And recently, superconductivity has been observed near room temperature in compounds alloyed with hydrogen, ”explains Professor Wang, director of the University’s Institute of Superconducting and Electronic Materials from Wollongong.

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THE STUDY

Experimental equipment: The diamond anvil cell (left) and hydrostatic pressure cell (right) can be used to establish the effect of pressure on the superconducting material.

“Pressure effects on iron-based superconductor families: superconductivity, flux pinning and vortex dynamics” has been published in Materials Today Physics in May 2021 (DOI 10.1016 / j.mtphys.2021.100414)

This work was supported by the Australian Research Council through the ARC Center of Excellence in FLEET.


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